I even tried to assign module to all K2 items, but with no luck. I used this code:

if (
$option == "com_k2"
and $view == "item"
) return 101;

I have no idea how to set it up. Do I need to buy Pro version for it? There are Advanced Module Manager, which would do what I need, but for this simple task I dont want to buy a component for 50 Euros (~70 USD). I would be more willing to spend 27 USD for MetaMod Pro.

As I didnt find any documentation on K2 assignment, could you guys help me with it?

You don't need the Pro version to get K2 support, but you may find issues with page formatting around the modules (or module positions not collapsing as they should if you're *not* on a K2 item page and that was the only module in the position) if you're just using the free version. Also take a look at the FAQs about that type of issue as sometimes there are ways around that even with the free version.

Best regards,
Stephen

Stephen BrandonMetaMod / Chameleon developerIf you use MetaMod or Chameleon, please post a rating and a review at the Joomla! Extensions Directory: Chameleon | MetaMod